The present invention relates to a manufacturing method for providing a roll, of the type used in a paper machine, with an exterior grooved surface, so that such a roll can be used with advantage in connection with dewatering operations carried out in a paper machine in a well known manner.
In particular, the present invention relates to a method according to which an elongated strip of suitable cross-sectional configuration is wound onto the exterior cylindrical surface of an inner roll body in such a way that the successive turns of the wound strip, which is initially straight, engage each other. The cross-sectional configuration of the strip is such that an outer edge region of the strip which is distant from the inner roll body has a thickness less than the thickness of the remainder of the strip. As a result the successive turns define between themselves at the outer edge region of the wound strip an elongated helical groove which provides the exterior grooved surface for the roll.
Manufacture of paper machine rolls with grooved exterior surfaces by winding onto the roll a steel strip or the like is already known. In this connection reference may be made to U.S. Pat. No. 3,718,959.
In order to manufacture rolls with exterior grooved surfaces, it has been customary to mount an inner roll body which has an exterior cylindrical surface on a machine similar to a lathe in such a way that this inner roll body can be driven in rotation about its axis. The carriage of the machine which is movable in a direction parallel to the axis about which the inner roll body is turned carries a structure which guides a strip to the outer surface of the rotating inner roll body as the latter rotates to pull the strip onto the roll body, this strip being previously provided with a suitable profile. Before the winding of the strip onto the exterior surface of the inner roll body is started, one end of the strip is fixed, as, for example, by welding, to a ring which is fixed to one end of the inner roll body.
In order that the strip will be wound on the roll body in such a way that it will provide a faultless covering of the inner roll body without any tendency to unwind therefrom, the successive turns of the strip must be placed tightly in engagement with the exterior surface of the roll body while each turn is urged intimately into engagement with the immediately preceding turn of the strip. However, it has been found from experience that when operations of this type are performed a serious drawback is encountered in that during winding of the strip in order to cover the inner roll body and particularly when the strip is tightened, or in other words tensioned, the outer edge region of the strip which is distant from the inner roll body tends to tilt away from the previously formed turns in a manner providing an undesirable space between each turn and the immediately preceding turn. This tendency of the strip to tilt away from a previously formed turn during the winding of the strip onto the inner roll body is enhanced by the fact that as a rule the cross-sectional configuration of the strip is such that the distance between the inner and outer edges of the strip, or in other words the radial dimension of the wound strip with respect to the axis of the inner roll body is considerably greater than the thickness of the strip in the axial direction of the inner roll body. For example, strips of the above type customarily will have a thickness on the order of 3 mm while the distance between the inner and outer edges of the strip, or in other words the above radial dimension thereof, is on the order of 12 mm. Of course, it is clear that the ultimate underlying reason for the tendency of the strip to tilt or tip in this way is that the strip is originally straight, but when applied to the cylindrical surface of the inner roll body must assume a curvature as required by the radius of the roll body, and this curving or bending of the strip to conform to the curvature of the inner roll body spreads outwardly from the inner toward the outer edge of the strip radially with respect to the axis of the inner roll body and in the direction of the longer dimension of the cross-sectional configuration of the strip. Of course, the result is that while some slight compression of the strip may take place along the inner edge region thereof which directly engages the exterior surface of the inner roll body, the outer edge region of the strip which is distant from this roll body must become elongated to a considerable degree during curving of the strip, and as a reaction to this latter tendency the strip tilts or tips in the manner described above in such a way that a turn of the strip which is being applied to the inner roll body tilts away from the previously formed turns.